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  • 1
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    Episodes of Particle Ejection from the Surface of the Active Asteroid (101955) Bennu (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-04
    Description: Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and SecurityRegolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN76455 , Science (ISSN 0036-8075) (e-ISSN 1095-9203); 366; 6470; eaay3544
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  • 2
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    Sub-Kelvin Cooling for Two Kilopixel Bolometer Arrays in the PIPER Receiver (2019)
    In:  Other Sources
    Details
    Publication Date: 2020-01-04
    Description: The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne telescope mission to search for inflationary gravitational waves from the early universe. PIPER employs two 32 40 arrays of superconducting transition-edge sensors, which operate at 100 mK. An open bucket Dewar of liquid helium maintains the receiver and telescope optics at 1.7 K. We describe the thermal design of the receiver and sub-Kelvin cooling with a continuous adiabatic demagnetization refrigerator (CADR). The CADR operates between 70 and 130 mK and provides 10 W cooling power at 100 mK, nearly five times the loading of the two detector assemblies. We describe electronics and software to robustly control the CADR, overall CADR performance in flightlike integrated receiver testing, and practical considerations for implementation in the balloon float environment.
    Keywords: Instrumentation and Photography; Engineering (General)
    Type: GSFC-E-DAA-TN75883 , Review of Scientific Instruments (ISSN 0034-6748) (e-ISSN 1089-7623); 90; 9; 095104
    Format: text
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  • 3
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    Cosmology Large Angular Scale Surveyor (CLASS) Focal Plane Development (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Cosmology Large Angular Scale Surveyor (CLASS) will measure the polarization of the Cosmic Microwave Background to search for and characterize the polarized signature of inflation. CLASS will operate from the Atacama Desert and observe approx.70% of the sky. A variable-delay polarization modulator provides modulation of the polarization at approx.10Hz to suppress the 1/f noise of the atmosphere and enable the measurement of the large angular scale polarization modes. The measurement of the inflationary signal across angular scales that spans both the recombination and reionization features allows a test of the predicted shape of the polarized angular power spectra in addition to a measurement of the energy scale of inflation. CLASS is an array of telescopes covering frequencies of 38, 93, 148, and 217 GHz. These frequencies straddle the foreground minimum and thus allow the extraction of foregrounds from the primordial signal. Each focal plane contains feedhorn-coupled transition-edge sensors that simultaneously detect two orthogonal linear polarizations. The use of single-crystal silicon as the dielectric for the on-chip transmission lines enables both high efficiency and uniformity in fabrication. Integrated band definition has been implemented that both controls the bandpass of the single-mode transmission on the chip and prevents stray light from coupling to the detectors.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN32347 , Journal of Low Temperature Physics (e-ISSN 1573-7357); 1-6
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  • 4
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    Fabrication of Feedhorn-Coupled Transition Edge Sensor Arrays for Measurement of the Cosmic Microwave Background Polarization (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Characterization of the minute cosmic microwave background (CMB) polarization signature requires multi-frequency high-throughput precision instrument systems. We have previously described the detector fabrication of a 40 gigahertz focal plane and now describe the fabrication of a 37-element dual-polarization detector module for measurement of the CMB at 90 gigahertz. The 72-TES (Transition Edge Sensor)-based bolometers in each module are coupled to a niobium-based planar orthomode transducer with integrated band defining filters implemented in microstrip transmission line. A single crystal silicon dielectric substrate serves as microstrip dielectric and as a thermal link between the membrane isolated MoAu TES operating at 150 millikelvins and the heat bath. A short silicon leg between the heat bath and the TES bolometer is designed for ballistic phonon transport and provides improved process control and uniformity of thermal conductance in the presence of phonon scattering on roughened surfaces. Micro-machined structures are used to realize the orthomode transducer backshort, provide out of band signal rejection, and a silicon photonic choke for feedhorn coupling are described. The backshort, choke wafer, and detector wafer are indium bump-bonded to create a single 37-element dual-polarization detector module. Fourteen such hexagonally shaped modules each 80 millimeters in size comprise two focal planes. These, along with the recently delivered 40 gigahertz focal plane, will survey a large fraction of the sky as part of the Johns Hopkins University-led ground-based CLASS (Cosmology Large Angular Scale Surveyor) telescope.
    Keywords: Electronics and Electrical Engineering; Instrumentation and Photography; Space Radiation
    Type: GSFC-E-DAA-TN24619 , International Workshop on Low Temperature Detectors; Jul 20, 2015 - Jul 24, 2015; Grenoble; France
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  • 5
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    Fabrication of Feedhorn-Coupled Transition Edge Sensor Arrays for Measurement of the Cosmic Microwave Background Polarization (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Characterization of the minute cosmic microwave background polarization signature requires multi-frequency high-throughput precision instrument systems. We have previously described the detector fabrication of a 40 GHz focal plane and now describe the fabrication of the detector modules for measurement of the CMB at 90GHz. The 74-TES based bolometers in each module are coupled to a niobium based planar orthomode transducer with integrated band defining filters implemented in microstrip transmission line. A single crystal silicon dielectric substrate serves as microstrip dielectric and as a thermal link between the membrane isolated MoAu TES operating at 150mK and the heat bath. A short silicon leg between the heat bath and the TES bolometer is designed for ballistic phonon transport and provides improved process control and uniformity of thermal conductance in the presence of phonon scattering on roughened surfaces. Micro-machined structures are used to realize the orthomode transducer backshort, provide out of band signal rejection, and a silicon photonic choke for feedhorn coupling are described. The backshort, choke wafer, and detector wafer are indium bump bonded to create a single 37-element dual-polarization detector module. Fourteen such hexagonally shaped modules each 90 mm in size comprise two focal planes. These, along with the recently delivered 40GHz focal plane, will survey a large fraction of the sky as part of the Johns Hopkins University led ground based CLASS (Cosmology Large Angular Scale Surveyor) telescope.
    Keywords: Space Radiation; Instrumentation and Photography; Electronics and Electrical Engineering
    Type: GSFC-E-DAA-TN26612
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  • 6
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    Recovery of Large Angular Scale CMB Polarization for Instruments Employing Variable-Delay Polarization Modulators (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Variable-delay Polarization Modulators (VPMs) are currently being implemented in experiments designed to measure the polarization of the cosmic microwave background on large angular scales because of their capability for providing rapid, front-end polarization modulation and control over systematic errors. Despite the advantages provided by the VPM, it is important to identify and mitigate any time-varying effects that leak into the synchronously modulated component of the signal. In this paper, the effect of emission from a 300 K VPM on the system performance is considered and addressed. Though instrument design can greatly reduce the influence of modulated VPM emission, some residual modulated signal is expected. VPM emission is treated in the presence of rotational misalignments and temperature variation. Simulations of time-ordered data are used to evaluate the effect of these residual errors on the power spectrum. The analysis and modeling in this paper guides experimentalists on the critical aspects of observations using VPMs as front-end modulators. By implementing the characterizations and controls as described, front-end VPM modulation can be very powerful for mitigating 1/ f noise in large angular scale polarimetric surveys. None of the systematic errors studied fundamentally limit the detection and characterization of B-modes on large scales for a tensor-to-scalar ratio of r= 0.01. Indeed, r less than 0.01 is achievable with commensurately improved characterizations and controls.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN40295 , The Astrophysical Journal (e-ISSN 1538-4357); 818; 2; 151
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  • 7
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    Overview of the Search for Space Weathering Signals on Bennu: One Rock Type, or Two? (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-13
    Description: We report on progress in the search for signs of space weathering on Bennu. We provide an overview of the space weathering evidence to date, and summarize relevant findings from several ongoing parallel studies of surface processes and surface properties. We examine trends from these studies in the context of space weathering, and what is known about near-Earth asteroid surface maturation. Because Bennu is covered with blocks, boulders, and rocks of various sizes, our search for space weathering signals has inevitably led to a study of the properties of Bennus rocks. Our research question is do Bennus bright and dark rock populations form a maturity continuum due to space weathering, or alternatively, do the bright and dark rocks provide compelling evidence for two distinct rock populations on Bennu? In particular, we present our best estimate of the sub-field-of-view OVIRS (OSIRIS-REx Visible and Infrared Spectrometer) spectral properties of the largest bright boulders and compare them with the darker materials on Bennus surface to see if the observed spectral and albedo differences are consistent with space weathering effects, or not.
    Keywords: Space Sciences (General)
    Type: JSC-E-DAA-TN73855 , Asteroid Science in the Age of Hayabusa2 and OSIRIS-REx; Nov 05, 2019 - Nov 07, 2019; Tucson, AZ; United States
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